Jupiter meets Mercury three times
Sagittarius answers to Jupiter, and both Gemini and Virgo answer to Mercury, while Pisces is classically Jupiter's second sign. So the whole difficulty list for Sagittarius is a quarrel between two planets: the one that generalises and the one that itemises.
Named plainly, the complaint runs in both directions. Mercury finds Jupiter's conclusions unearned; Jupiter finds Mercury's qualifications endless. That is a genuine and recognisable difference in how people argue, and it has nothing to do with the month anyone was born in once you look at where Mercury and Jupiter actually fall.
The angles that generate the list
Gemini lies 180 degrees from Sagittarius. Pisces and Virgo lie 90 degrees away on either side. Those are the only hard aspects available, which is why the same three names appear on every version of this list.
All four signs are mutable, closing their seasons. The friction between them is therefore restless rather than immovable: plans change, subjects change, and the disagreement recurs in an altered shape instead of coming to a head.
An opposition is a shared question
Signs at either end of an axis hold the same mode and divide one subject. Sagittarius and Gemini split knowledge between the general and the particular, which is why the pairing appears constantly in long friendships and marriages and not only in cautionary lists.
The angle fixes the topic. It has nothing to say about whether two people find the division useful, and any list implying otherwise is overreaching.
What produces real strain
Difficulty in a comparison sits in contacts between personal points. One person's Saturn on the other's Moon or Venus is the heavy one. Neptune touching a personal planet leaves things unclear, which for a Sagittarius chart usually shows up as promises understood differently by each party. Close Mars contacts describe the tempo of a row.
Exactness is decisive and sun signs supply none of it: a Sagittarius sun at one degree does not square a Virgo sun at twenty-eight in any meaningful sense. The synastry calculator reads the true separations from two birth times, and synastry explains the weighting.
Better than a place on a list
The Sagittarius and Gemini page describes what the axis handles well and where it tires, and the Virgo page does the same for the square. Either is more informative than a ranking assembled from angles.
Where both birth times are known, compare the charts. Suns that are supposed to clash often share close Moon or Venus contacts, and that fact is invisible from birthdays alone.
Questions people ask about this
Which signs are hard for Sagittarius?
Gemini opposite, Pisces and Virgo square. All are mutable signs, as Sagittarius is.
Is Gemini a bad match for Sagittarius?
Not on the angle. The two hold opposite ends of one axis, which the tradition reads as attraction at least as often as conflict.
Why do Mercury and Jupiter dominate this page?
They rule every sign on the list, so the friction described is really one planetary contrast repeated.
What genuinely predicts trouble?
Saturn or Neptune on the other person's personal planets, hard Mars contacts, and tight orbs.